Method and apparatus for manufacturing slalom false twisting on ring yarn

ABSTRACT

In a process for manufacturing a singles ring yarn, a method and apparatus is invented which utilizes double belts as a false twist device and incorporates it in the conventional ring spinning machine for producing a singles ring yarn. In this invention, a double-belts is applied thus two twisting points, instead of one twisting point, are adopted for the yarn false twisting to improve the false twist efficiency. Accordingly, a ratio of the velocity of the belt to the delivery speed of the yarn is controlled and the wrapping angle of the yarn on the belts is adjusted in order to obtain the desired property of the final singles ring yarn. The said invention can enhance the strength of fiber strand at the spinning triangle and thus ensure the yarns spun in a normal condition at low twist multipliers, which is unable to be obtained by the conventional ring spinning machine. The method produces yarns with good strength, less hairiness and lower yarn residual torque at low twist level and endows the resultant fabric with softer handle, low spirality as well as clear and smooth surface appearance. The method and apparatus has the advantages of easy yarn piecing-up and doffing process, low spinning end-breakage when using ordinary raw materials and low cost of investment and maintenance, which not only is able to meet the commercial requirements of the large-scale production in the textile industry but also possesses a high false twist efficiency.

BACKGROUND

1. Field of the Invention

The present invention relates to spinning technology for the productionof a singles ring yarn. The invention is particularly concerned with amethod and apparatus that utilizes a false twist device with two falsetwisting points to nip yarns between double belts and incorporates it inthe conventional ring spinning machine to improve yarn property andfabric performance as well as the efficiency of false twist and easinessof the operation. The false twist efficiency for yarn and thus theproperty of the final singles ring yarn can be controlled.

2. Background of the Invention

Twisting is an important step of short fiber spinning. In this process,the yarns, are elastically twisted and transformed to attain sufficientstrength, wear resistance and smoothness. However, as a negative effect,a large amount of residual torque or twist liveliness is also broughtabout in the yarns simultaneously. Such twist liveliness of the yarnsrenders a significant influence on the possessing quality of the latterproducts. For example, if yarns with twist liveliness are used forknitting, loops of the fabric will lose their balance because of theresidual torque in the yarns. In order to attain the natural structurewith the minimum energy condition, the loops tend to rotate to releasethe internal torsion stress. As a result, one end of the loops will tiltand protrude from the fabric surface, while the other end will stayinside the fabric. Such deformation of the loops will increase thespirality of the fabric, i.e., a deformation similar to the rib effect,which should be prevented to the utmost in the spinning industry. Thus,the balancing of torque inside the yarns is particularly important.

Staple yarns are made from a large quantity of fibers bounded by theirfriction inbetween. Hence, the residual torque of the yarns or thespirality of the fabric is mainly affected by said characteristic of thefibers, such as the type and cross sectional shape of the fibers, thepolymerizing manner of the fibers and the internal structure of theyarns, etc.

First of all, different types of fibers have a different modulus andcross sectional shape, thus lead to different degree of stress in theyarns. In the cotton/polyester blended yarns, increasing the ratio ofpolyester will enhance the twist liveliness of rotor and ring yarns,heat setting can improve the spirality of the resultant fabrics. This isbecause polyester has a higher modulus, and said two types of fiber havedifferent cross sectional shapes.

Next, different yarn structures have a different distribution of stress.Experimental results, such as Barella and Manich in the Textile ResearchJournal, Vol. 59, No. 12, 1989, Lord and Mohamed in the Textile ResearchJournal, Vol. 44, No. 7, 1974 and Sengupta, and Sreenivasa in theTextile Research Journal, Vol. 64, No 10, 1994 showed that, frictionyarns (DREF-II) have the largest residual torque and trend ofdeformation in the priority sequence followed by ring yarns, rotor yarnsand air-jet yarns. It is generally agreed that single ring yarns arecomposed of a plurality of uniformly enveloped concentric helicalthreads, while fiber migration is a secondary feature. Hence, when thering yarns are reverse-twisted, their strength will gradually decreasesto zero, by then the yarns will be all dispersed. In relation to ringyarns, unconventional spinning systems produce yarns with core-sheathstructures, such as rotor spinning yarn, air jet spinning yarn andfriction spinning yarns. The packing density of said yarns is uneven andmainly characterized in the partial entanglement and entrapment of thefibers.

In addition, many factors can affect the degree of movement freedom ofthe loops of the fabric and also the final spirality of the fabric. Saidfactors include fabric structure, parameters of the knitting machine,and the fabric relaxation and fabric setting due to finishing. All theaforesaid factors affecting the spirality of fabric were reported indetail by Lau and Tao in the Textile Asia, Vol. XXVI, No. 8, 1995.

Same as other materials, the residual torque of the yarns can be reducedor eliminated with different methods. In the past several decades, avariety of torque balancing methods have been developed. According tothe basic theory, they can generally be split into two categories:permanently processing methods and physical torque balancing methods.

Permanently setting methods mainly accomplish the purpose of releasingresidual torque by transforming the elastic torsional deformation intoplastic deformation. The method mainly relates to a variety of settingtechniques for material, such as thermal setting, chemical processingand wet setting etc. In the Textile Research Journal, Vol. 59, No. 6,1989, Araujo and Smith have proved that for air-jet and rotor yarns, theheat setting of single cotton/polyester blended yarns can effectivelyreduce the residual torque of the yarn. However, in relation to naturalfibers such as cotton or wool, permanent setting is too complicated. Itmay involve steaming, hot water and chemical processing (such asmercerization in the case of cotton yarns and treatment with sodiumbisulphite in the case of the wool yarns). In addition, in relation tonatural yarns, setting cannot completely eliminate the residual torqueof the single yarns, and it may also cause damage to the yarns.

Compared with permanent processing, physical torque balancing is a puremechanical processing technique. The main point of the method is tofully utilize the structure of yarns to balance the residual torquegenerated in different yarns while maintaining the elastic deformationcharacteristic of the yarns. Currently in the industry, separatemachines are required to enforce torque balancing of the yarns hence thecost is higher. The method comprises plying two identical singles yarnswith a twist equal in number but in the opposite direction to that inthe singles yarns; or feeding two singles yarns with twist of the samemagnitude but in opposite direction onto the same feeder.

Recently, some new torque balancing methods for yarns also emerged inthe Textile Research Journal, Vol. 65, No. 9, 1995, Sawhney and Kimmeldescribed a series spinning system for processing torque-free yarns. Theinner core of said yarns is formed by processing with an airjet systemwhile outside the core is enwrapped with crust fibers similar toDREF-III yarns. In the Textile Research Journal, Vol. 62, No. 1, 1992,Sawhey etc. have suggested a method of processing ring cottoncrust/polyester inner core yarns. Said yarns accomplish balancingcondition by utilizing core yarns with opposite twisting direction fromsynthetic yarns, or applying heat processing on the polyester portion ofsaid yarns. However, it is readily seen that the machines and processingtechniques related to the aforesaid method are generally morecomplicated. In the Textile Research Journal, Vol, 57, No. 10, 1997, Taohas processed the layer structure of the inner core-crust of rotor yarnsto generate torque-free single yarns, yet said technique is not suitablefor ring yarns.

In addition, U.S. Pat. No. 6,860,095 B2, filed by Tao et al. discloses amethod of producing torque-free singles ring yarns. According to thispatent application, a draft fiber is divided into a plurality ofsub-assemblies of fibers. Each sub-assembly of fibers firstly attains anindividual twist value during a false twisting, and then are twistedtogether to form the final yarns. The false twisting is controlled suchthat balance of the internal torque of the final yarns is achieved.Furthermore, U.S. Pat. No. 7,096,655 B2 filed by Tao et al. discloses amethod and apparatus for producing a singles ring yarn. In this method,a false twist device rotates at a first speed for twisting the fibers.Immediately after the first twisting step, a joint twist of the secondtwist in the same direction as the first twist and a third twist in areversed direction is supplied to the preliminary yarn for producingfinal singles ring yarn. Moreover, a ratio of first speed to the secondspeed is controlled for controlling the residual torque in the finalsingles ring yarn.

The aforementioned patents present the method and apparatus for singlesring yarn. However, the abovementioned patent application is moreappropriate for torque-free singles ring yarn production in thelaboratory scale. The yarn piecing-up and doffing process can notcompletely be able to meet the practical requirements of the largescaleproduction in the textile industry. Furthermore, the spinningend-breakage when using ordinary cotton and the cost of investment andmaintenance need to be further reduced for the widely commercialapplication. In order to overcome the above shortcomings, two twistingpoints, instead of one twisting point, are adopted for the yarn falsetwisting to obtain the high false twist efficiency in this invention. Inaddition, a ratio of the velocity of the belt to the delivery speed ofthe yarn is controlled and the wrapping angle of the yarn on the beltsis adjusted in order to obtain the desired property of the final singlesring yarn.

OBJECT OF THE INVENTION

Therefore, it is an objective of the present invention to provide animproved method and apparatus for producing singles ring yarns. Themethod and apparatus has the actual advantages of easy yarn piecing-upand doffing process, low spinning endbreakage when using ordinary rawmaterials and low cost of investment and maintenance, which not only isable to meet the commercial requirements of the large-scale productionin the textile industry but also possess high false twist efficiency,wherein instead of one twisting point, two twisting points are adoptedfor the yarn false twisting to improve the false twist efficiency, andwherein the false twist efficiency is controlled such that the desirablelower residual torque as well as other yarn properties can be achieved.Accordingly, a ratio of the velocity of the belt to the delivery speedof the yarn is controlled and the wrapping angle of the yarn on thebelts is adjusted in order to obtain the desired property of the finalsingles ring yarn.

SUMMARY OF THE INVENTION

According to an aspect of present invention, a method for producingsingles ring yarns is as follows.

A first high twist is imparted to a strand of traveling drafted fibersemerged from the front-drafting-roller nip with the upper belt of afalse twist device for producing a preliminary singles yarn, wherein thebelt travels at the velocity of the belt for twisting the fibers andthus the strength of fiber strand is enhanced at the spinning trianglewhen a low twist level is adopted in the final singles yarn. Immediatelyafter the false twist step by the upper belt severed as the firsttwisting point, a joint twist of a second twist in the same direction asthe first twist and a third twist in the reversed direction are impartedto the preliminary singles yarn for the production of a final singlesring yarn, wherein the second twist is produced by a running of thelower belt on the yarn, wherein the third twist results incorrespondence to the first twist by a running of the upper belt on theyarn. Immediately after the false twist step by the lower belt severedas the second twisting point, a joint twist of a forth twist in the samedirection as the second twist, and a fifth twist in the reverseddirection are imparted to the preliminary singles yarn for theproduction of a final singles ring yarn, wherein the forth twist isproduced by a rotatable take-up package of the ring spinning machineonto which the final singles yarn is drawn, wherein the fifth twistresults in correspondence to the second twist by a running of the lowerbelt on the yarn. Then the final singles yarn was drawn onto the take-uppackage. The upper and lower belts run in the same velocity.

Controlling a ratio of the velocity of the belts to the delivery speedof the yarn and the wrapping angle of the yarn on the belts can controlthe false twist efficiency for yarn and thus the yarn property.

According to another aspect of present invention, an apparatus forproducing singles ring yarns is as follows.

The upper belt of a false twist device travelling at the velocity of thebelt imparts a first high twist to a strand of travelling drafted fibersemerged from the front-drafting roller nip such that a preliminarysingles yarn is produced. The lower belt of a false twist devicetravelling at the same velocity as the upper belt imparts a second twistin the same direction as the first twist to a preliminary singles yarnemerged from the upper belt such that a further preliminary singles yarnis produced. A rotatable take-up package onto which the final singlesyarn is drawn imparts a fourth twist in the same direction as the firsttwist and second twist to a preliminary singles yarn emerged from thelower belt such that final singles yarn is produced, wherein the doublebelt travels at the velocity of the belt for twisting the fibers andthus the strength of fiber strand is enhanced at the spinning trianglewhen a low twist level is adopted in the final singles yarn, wherein ajoint twist of a second twist in the same direction as the first twistand a third twist in the reversed direction are imparted to thepreliminary singles yarn for the production of a final singles ringyarn, wherein the second twist is produced by a running of the lowerbelt on the yarn, wherein the third twist results in correspondence tothe first twist by a running of the upper belt on the yarn, wherein theyarn was drawn onto the take-up package at the delivery speed of theyarn, wherein a joint twist of a forth twist in the same direction asthe second twist and a fifth twist in the reversed direction areimparted to the preliminary singles yarn for the production of a finalsingles ring yarn, wherein the forth twist is produced by a rotatabletake-up package onto which the final singles yarn is drawn, and whereinthe fifth twist results in correspondence to the second twist by arunning of the lower belt on the yarn.

A ratio of the velocity of the belts to the delivery speed of the yarncan be controllable and the wrapping angle of the yarn on the belts isadjustable such that the false twist efficiency and the yarn propertycan be adjusted.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, which description illustrates by way of examplethe principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side diagrammatic plan view of a spinning apparatus inaccordance with an exemplary embodiment of the present invention;

FIG. 2 is a schematic representative in perspective, of a spinningapparatus in accordance with an exemplary embodiment of the presentinvention;

FIG. 3 is a side enlargement of part of FIG. 1 showing the geometryinterrelations of the yarn, the upper belt and lower belt;

FIG. 4 is alternative of a side diagrammatic plan view of a spinningapparatus in accordance with an exemplary embodiment of the presentinvention with a nip false twister consisting of the two belts;

FIGS. 5A and 5B are two alternatives of a side diagrammatic plan view ofa spinning apparatus of an exemplary embodiment of the present inventionshown in FIG. 1 with core spandex/filament;

FIGS. 6A and 6B are two alternatives of a side diagrammatic plan view ofa spinning apparatus of an exemplary embodiment of the present inventionshown in FIG. 4 with core spandex/filament;

FIG. 7 is an alternative of a side diagrammatic plan view of a spinningapparatus of an exemplary embodiment of the present invention with twobelts running in cross direction and regulation block;

FIG. 8 is another alternative of a side diagrammatic plan view of aspinning apparatus of an exemplary embodiment of the present inventionwith two belts driving individually and running in cross direction;

FIG. 9 is another alternative of a top diagrammatic plan view of aspinning apparatus in accordance with an exemplary embodiment of thepresent invention with a nip false twister consisting of the two beltsarranged in concentric circle;

FIG. 10 illustrates ten alternatives of a cross-sectional profile of thefalse twist belt shown in FIGS. 1-9;

FIG. 11 is a diagrammatic view of the modified curves of verticalpositions relative to time of a ring for yarn doffing.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a side diagrammatic plan view and a schematicrepresentative in perspective of a spinning apparatus in accordance withan exemplary embodiment of the present invention, respectively. As shownin FIGS. 1 and 2, a roving 101 is delivered through the drafting system103, 105 and 107, including a pair of back drafting rollers 103, a pairof aprons 105, and a pair of front drafting rollers 107. The draftedroving is twisted by the upper belt 111 of a false twist device 102 toform a preliminary singles yarn wherein the false twist for a yarn isprovided by the running action of the upper belt 111. Immediately afterthe false twist step by the upper belt 111 severing as the firsttwisting point, a joint twist of a second twist in the same direction asthe first twist and a third twist in the reversed direction are impartedto the preliminary singles yarn 106 for the production of a finalsingles ring yarn, wherein the second twist is produced by a running ofthe lower belt 113 on the yarn, wherein the third twist results incorrespondence to the first twist by a running of the upper belt 111 onthe yarn.

Immediately after the false twist step by the lower belt 113 severing asthe second twisting point, a joint twist of a forth twist in the samedirection as the first twist and second twist, and a fifth twist in thereversed direction are imparted to the preliminary singles yarn for theproduction of a final singles ring yarn 104, wherein the forth twist isproduced by a rotatable take-up package 121 onto which the final singlesyarn is drawn, wherein the fifth twist results in correspondence to thesecond twist by a running of the lower belt 113 on the yarn. Then theyarn 104 proceeds to a yarn guide 115, and then further to a bobbin 121.The yarn 104 becomes wound on the bobbin 121 via a traveler 117 movingon a ring rail 119.

As shown in FIGS. 1 and 2, the double-belts twisting device 102includes, in addition to other components, primarily an upper belt 111and a lower belt 113. In the false twisting device 102, the upper belt111 and the lower belt 113 are travelling in opposite directions withthe same velocity. The yarn 109 interacts with the false twisting device102 in a slalom-like arrangement with two false twisting points, i.e.,the yarn 109 interacts with the outer surface on one belt which seversas the first twisting point, then interacts on the inner surface of theother belt which severs as the second twisting point. In this case, theyarn 109 interacts with the outer surface of the upper belt 111 firstthen diverges to the inner surface of the lower belt 113, before exitingthe false twister. In fact, the yarn is false twisted by the torquegenerated by running the double belts in opposite travelling directions.

Furthermore, in the exemplary embodiment, there are two false twistingpoints of a false twist device by the travelling upper belt and lowerbelt for the yarn. The false twist efficiency for the yarn depends onthe friction between the yarn and the surface of the upper belt andlower belt, and the ratio of the velocity of the belts to the deliveryspeed of the yarn. The residual torque and other yarn properties of thefinal singles ring yarn are controlled by controlling the frictionbetween the yarn and the surface of the upper belt and lower belt, andthe ratio of the velocity of the belts to the delivery speed of theyarn.

The belt can be driven by a conveyor belt 209 having two or more pulleys207, whereby at least one of the pulleys 207 is attached to a motor 211.The motor 211 is controlled by suitable electronics such as inverters213. The motor 211 has the capability to drive the conveyor belt andfurther drive the double belts with a controllable ratio of the velocityof the belts to the delivery speed of the yarn predetermined by thedesired impartation of false twist and thus the resultant amount of aresidual torque as well as other yarn performance in the final singlesring yarn.

An additional yarn guide 110 installed above the upper belt 111 for eachspindle is used to control the yarn movement during the spinning. Thepositioning of the yarn guide 110 should be aware in the installation.Exceed amount of friction between yarn guide and yarn results in theyarn breakage where insufficient amount of false twist results in thepoor yarn strength. Several belt guides 203, installed on the both sidesof the double belts 111 and 113, and several pressuring discs 201,installed on upper and below sides of the belts 111 and 113, are used tocontrol the belts movement, as well as adjust the geometryinterrelations of the yarn and the upper belt and lower belt and thetension of the belts. Through the belt guides 203, pressuring discs 201and the wheels 205, the belts are maintained in a stable condition withpredetermined tension. FIG. 3 is a side enlargement of part of FIG. 1showing the geometry interrelations of the yarn, the upper belt 111 andlower belt 113; As shown in FIG. 3, “_(—) ₁ ”, “_(—) ₂ ” and “_(—) ₃ ”represent the crossing angles of the straight line (O₁O₂) with respectto the travelling path of the yarn portions 109, 106 and 104respectively, wherein “O₁” is the center of the upper belt and “O₂” isthe center of the lower belt. “_(—) ₁ ” and “_(—) ₂ ” represent thewrapping angles of yarn portions on the upper belt and lower belt,respectively. “L” represents the length of the straight line whichconnects the center (O₁) of the upper belt and the center (O₂) of thelower belt. The geometry interrelation of the yarn, the upper belt andlower belt which is described by the crossing angles (_(—) ₁ , _(—) ₂and _(—) ₃ ), wrapping angles (_(—) ₁ and _(—) ₂ ) and the length of thestraight line (O₁O₂) is important in determining the optimal adaptationof the double-belts false twist device to the desired impartation offalse twist, and in optimizing the yarn tension conditions. FIG. 4 isalternative of a side diagrammatic plan view of a spinning apparatus inaccordance with an exemplary embodiment of the present invention with anip false twister 102 consisting of the two belts. As shown in FIG. 4,the drafted roving is twisted by being contacted from opposite sides bythe travelling upper belt 111 and lower belt 113 of a false twist device102 to form a preliminary singles yarn wherein the false twist for ayarn is provided by the running action of the upper belt and lower belt113 travelling in opposite direction. FIG. 4 provides the false twistdevice with one twisting point instead of two twist points shown inFIG. 1. Compared to the one belt false twisting device, the nip falsetwister can increase the pressure between the yarn and the belts.

FIGS. 5A and 5B are two further embodiments of apparatus of the presentinvention as well as method shown in FIG. 1 for the corespandex/filament yarn. FIG. 5A provides an apparatus of the presentinvention for the core spandex/filament singles ring yarn. Thespandex/filament 501 is delivered by feed rollers 503 and turningrollers 505 and then fed into the front rollers 107. The draft ratio iscontrolled by the surface speed ratio of the front rollers 107 to thefeed rollers 503. FIG. 5B provides another apparatus of the presentinvention for the core spandex/filament singles ring yarn. Thespandex/filament 501 is also delivered by feed rollers 503 and turningrollers 505 and then fed into the drafting system including a pair ofback drafting rollers 103, a pair of aprons 105, and a pair of frontdrafting rollers 107. The draft ratio is controlled by the draft ratioof the drafting system and the surface speed ratio of the back rollers103 to the feed rollers 503. Emerging from the front roller nip, thecore spandex/filament and fibers twisted together by running the beltsof the false twist device 102 and then rotating the take-up package 121to form the final core spandex/filament singles ring yarn 104.

FIGS. 6A and 6B are other two further embodiments of apparatus of thepresent invention as well as method shown in FIG. 4 for the corespandex/filament yarn. FIG. 6A provides an apparatus of the presentinvention for the core spandex/filament singles ring yarn. Thespandex/filament 501 is delivered by feed rollers 503 and turningrollers 505 and then fed into the front rollers 107. The draft ratio iscontrolled by the surface speed ratio of the front rollers 107 to thefeed rollers 503. FIG. 6B provides another apparatus of the presentinvention for the core spandex/filament singles ring yarn. Thespandex/filament 501 is also delivered by feed rollers 503 and turningrollers 505 and then fed into the drafting system including a pair ofback drafting rollers 103, a pair of aprons 105, and a pair of frontdrafting rollers 107. The draft ratio is controlled by the draft ratioof the drafting system and the surface speed ratio of the back rollers103 to the feed rollers 503. Emerging from the front roller nip, thecore spandex/filament and fibers twisted together by running the beltsof the false twist device 102 and then rotating the take-up package 121to form the final core spandex/filament singles ring yarn 104.

FIG. 7 is another embodiment of apparatus of the present invention aswell as method with double belts running in cross direction andregulation block for the friction adjusting between the yarn and belts.As shown in FIG. 7, the outer face of the outer belt 701 is disposed inan opposing, substantially non-contacting relationship with the outerface of the inner belt 703, and defines a gap there between. A yarn 109is advanced along the line which bisects the angle formed by the twocrossing belts, and through the twisting zone composed of the opposingbelts 701 and 703 overlapped. The belts are pressed against the yarn inthe area of the twisting zone by the regulation block 705 which consistsof spring and shim assembly. The regulation block can adjust thefriction between the yarn and belts, improve the control of fibermovement during the false twisting of the yarn, provide an easier yarnpiecing process as well as increase the false twist efficiency.

FIG. 8 is another alternative of a side diagrammatic plan view of aspinning apparatus of an exemplary embodiment of the present inventionwith two belts driven individually and running in cross direction; Asshown in FIG. 8, the outer face of the outer belt 801 is disposed in anopposing, substantially non-contacting relationship with the outer faceof the inner belt 803, and defines two gaps there between. A yarn 109 isadvanced along the line which bisects the angle formed by the twocrossing belts, and through the twisting zone composed of the opposingbelts 801 and 803 overlapped. FIG. 8 provides the false twist devicewith two twisting point instead of one twist points shown in FIG. 7.Compared to the false twist device shown in FIG. 7, the false twistdevice shown in FIG. 8 can adjust the contact area between the yarn andbelts to further improve the control of fiber movement during the falsetwisting of the yarn, increase the false twist efficiency as well asprovide an much easier yarn piecing process.

FIG. 9 is another alternative of a top diagrammatic plan view of aspinning apparatus in accordance with an exemplary embodiment of thepresent invention with a nip false twister consisting of the two beltsarranged in concentric circle. As shown in FIG. 9, the yarn 109 is falsetwisted by the running action of outer belt 901 and inner belt 903travelling in opposite direction in a false twist device to form apreliminary singles yarn. The outer belt 901 and inner belt 903 can bedriven individually in high velocity as well as in more stable runningcondition to increase the false twist efficiency. FIG. 10 illustratesten alternatives of a cross-sectional profile of the false twist beltshown in FIGS. 1-9. The belt profile particularly the shape of thecontacting section of the belt with the yarn, the hardness as well asthe surface property of the belt are important for false twistingeffects. The round shape and elliptical shape illustrated by thecross-sectional profiles 1001 and 1003 for the belt are two desirablecontacting shapes with the yarn during the yarn false twisting. Thecross-sectional profile 1001′ and 1003′ for the belt are another twoalternatives with hollow inside the belt which results in the reductionof hardness of the belt and thus changes the friction between the yarnand the belt. All these four types of belt shapes can be used for theyarn false twisting process showed in FIGS. 1-6, and which one is to beused mainly depends on the required false twisting effects. Thecross-sectional profiles 1005, 1007 and 1009 are the other three shapesfor the belt and the cross-sectional profiles 1005′, 1007′ and 1009′ aretheir corresponding three alternatives with hollow inside the belt,wherein the top shape is for the contacting area of the belt with theyarn. All these six types of belt shapes can be used for the yarn falsetwisting process showed in FIGS. 7-9. FIG. 11 is a diagrammatic view ofthe modified curves of vertical positions relative to time of a ring foryarn doffing. The modifications have been proposed on the conventionaldoffing process to avoid yarn snap during doffing process. In FIG. 11,1101 and 1103 are respectively the modified curves of the mean verticalposition and the resultant vertical position of the ring rail. Two axesof the coordinates represent time 1105 and vertical position 1107,respectively. According to an exemplary embodiment of the presentinvention, the spinning apparatus is powered off at time 1109 whichshould be matched to the power off time of the motor 211 when the ringrail moves upwards to the up-most position. Thereafter, the ring rail iswaited for a predetermined period of time 1111. Then it is finallypulled down the ring gradually at the winding time 1115 until the ringcompletely stops at the termination time 1117, wherein 1113 indicatesthe total stop period of time.

1. A method for producing singles ring yarns, comprising: imparting a first high twist to a strand of traveling drafted fibers emerged from the front-drafting-roller nip with the upper belt of a false twist device for producing a preliminary singles yarn, wherein the belt travels at the velocity of the belt for twisting the fibers and thus the strength of fiber strand is enhanced at the spinning triangle when a low twist level is adopted in the final singles yarn; immediately after the false twist step by the upper belt severed as the first twisting point, imparting a joint twist of a second twist in the same direction as the first twist and a third twist in the reversed direction to the preliminary singles yarn for the production of a final singles ring yarn, wherein the second twist is produced by a running of the lower belt on the yarn, wherein the third twist results in correspondence to the first twist by a running of the upper belt on the yarn; immediately after the false twist step by the lower belt severed as the second twisting point, imparting a joint twist of a forth twist in the same direction as the second twist, and a fifth twist in the reversed direction to the preliminary singles yarn for the production of a final singles ring yarn, wherein the forth twist is produced by a rotatable take-up package of the ring spinning machine onto which the final singles yarn is drawn, wherein the fifth twist results in correspondence to the second twist by a running of the lower belt on the yarn; then the final singles yarn was drawn onto the take-up package; running the upper and lower belts in the opposite directions with the same velocity; and controlling a ratio of the velocity of the belts to the delivery speed of the yarn and the wrapping angles of the yarn on the double-belts for controlling the false twist efficiency for yarn and thus the yarn property.
 2. The method for producing singles ring yarns of claim 1, wherein the yarn interacts with the false twisting device in the form of two false twisting points and in fact the yarn is false twisted by the torque generated by running the double belts in opposite travelling directions with the same velocity.
 3. The method for producing singles ring yarns of claim 1, wherein the geometry interrelation of the yarn, the upper belt and lower belt is important in determining the optimal adaptation of the double belts false twist device to the desired impartation of false twist, and in optimizing the yarn tension conditions and false twist efficiency.
 4. The method for producing singles ring yarns of claim 1, wherein the residual torque and other yarn properties of the final singles ring yarn are controlled by controlling the friction between the yarn and the surface of the upper belt and lower belt, and the ratio of the velocity of the belts to the delivery speed of the yarn.
 5. The method for producing singles ring yarns of claim 1, wherein the high false twist efficiency that utilizes double belts as a false twist device is provided during the yarn spinning process, and wherein the ordinary raw materials can be used to produce singles ring yarn due to the improved strength of fiber strand in the spinning triangle and the improved fiber inter-friction within the yarn at a low twist level.
 6. An alternative method for producing singles ring yarns, comprising: imparting a first high twist to a strand of traveling drafted fibers emerged from the front-drafting-roller nip with a nip false twister consisting of the two belts in close position for producing a preliminary singles yarn, wherein the false twist device provides one twisting point instead of two twist points for a yarn, wherein the false twist device provides more false twist efficiency than that of one belt false twist device, and wherein the yarn is false twisted by the torque generated by running the double belts in opposite travelling directions with the same velocity.
 7. An another alternative method for producing singles ring yarns, comprising: imparting a first high twist to a strand of traveling drafted fibers emerged from the front-drafting-roller nip with double belts running in cross direction and regulation block for the friction adjusting between the yarn and belts for producing a preliminary singles yarn, wherein a yarn is advanced along the line which bisects the angle formed by the two crossing belts, i.e., the false twisting zone.
 8. The method for producing singles ring yarns of claim 7, wherein the belts are pressed against the yarn in the area of the twisting zone by the regulation block which consists of spring and shim assembly, and wherein the regulation block can adjust the friction between the yarn and belts, improve the control of fiber movement during the false twisting of the yarn as well as provide a easier yarn piecing process.
 9. An apparatus for producing singles ring yarns, comprising: the upper belt of a false twist device travelling at the velocity of the belt imparting a first high twist to a strand of travelling drafted fibers emerged from the front drafting-roller nip such that a preliminary singles yarn is produced; the lower belt of a false twist device travelling at the same velocity as the upper belt imparting a second twist in the same direction as the first twist to a preliminary singles yarn emerged from the upper belt such that a further preliminary singles yarn is produced; a rotatable take-up package onto which the final singles yarn is drawn imparting a fourth twist in the same direction as the first twist and second twist to a preliminary singles yarn emerged from the lower belt such that final singles yarn is produced, wherein the double belt travels at the velocity of the belt for twisting the fibers and thus the strength of fiber strand is enhanced at the spinning triangle when a low twist level is adopted in the final singles yarn, wherein a joint twist of a second twist in the same direction as the first twist and a third twist in the reversed direction are imparted to the preliminary singles yarn for the production of a final singles ring yarn, wherein the second twist is produced by a running of the lower belt on the yarn, wherein the third twist results in correspondence to the first twist by a running of the upper belt on the yarn, wherein the yarn was drawn onto the take-up package at the delivery speed of the yarn, wherein a joint twist of a forth twist in the same direction as the second twist and a fifth twist in the reversed direction are imparted to the preliminary singles yarn for the production of a final singles ring yarn, wherein the forth twist is produced by a rotatable take-up package onto which the final singles yarn is drawn, and wherein the fifth twist results in correspondence to the second twist by a running of the lower belt on the yarn, wherein the ratio of the velocity of the belts to the delivery speed of the yarn can be controllable and the wrapping angle of the yarn on the belts is adjustable such that the false twist efficiency and the yarn property can be adjusted.
 10. The apparatus of claim 9, wherein the false twisting device mainly comprise the double belts severed as two false twisting points when the double belts travel in opposite travelling directions with the same velocity.
 11. The apparatus of claim 9, wherein the belt guides and pressuring discs are used to control the belts movement, as well as adjust the geometry interrelations of the yarn and the upper belt and lower belt and the tension of the belts.
 12. An alternative apparatus for producing singles ring yarns, comprising: a nip false twister consisting of the two belts in close position imparting a first high twist to a strand of traveling drafted fibers emerged from the front-drafting-roller nip for producing a preliminary singles yarn, wherein the false twist device provides one twisting point instead of two twist points for a yarn, and wherein the yarn is false twisted by the torque generated by running the double belts in opposite travelling directions with the same velocity.
 13. An another alternative apparatus for producing singles ring yarn, comprising: a false twist device with double belts running in cross direction imparting a first high twist to a strand of traveling drafted fibers emerged from the front-drafting-roller for producing a preliminary singles yarn, wherein a yarn is advanced along the line which bisects the angle formed by the two crossing belts, i.e., the false twisting zone.
 14. The apparatus of claim 13, wherein the belts are pressed against the yarn in the area of the twisting zone by the regulation block which consists of spring and shim assembly, and wherein the regulation block can adjust the friction between the yarn and belts, improve the control of fiber movement during the false twisting of the yarn as well as provide a easier yarn piecing process.
 15. The apparatus of claim 9, wherein ten different types of belt shapes such as round shape, elliptical shape and with/without hollow inside the belt for the false twist device can be used for the yarn false twisting process and which one is to be used mainly depends on the required false twisting effects.
 16. The apparatus of claim 12, wherein ten different types of belt shapes such as round shape, elliptical shape and with/without hollow inside the belt for the false twist device can be used for the yarn false twisting process and which one is to be used mainly depends on the required false twisting effects.
 17. The apparatus of claim 13, wherein ten different types of belt shapes such as round shape, elliptical shape and with/without hollow inside the belt for the false twist device can be used for the yarn false twisting process and which one is to be used mainly depends on the required false twisting effects. 